Twelve-year-old Morgan Geyser, above, and another girl will be tried as adults this fall in the stabbing of a classmate in the so-called Slenderman case in Wisconsin. Both girls reportedly were obsessed with the evil fictional character. The girl they allegedly stabbed survived. (Getty Images/Milwaukee Journal-Sentinal/Michael Sears)

Youth advocates are seizing on bipartisan interest in criminal justice reform and historically low crime rates to lobby states to lighten sentencing standards for juveniles. They also advocate more efforts to prepare troubled teenagers — even those convicted of the most violent crimes — to be productive members of society. In 2012 the U.S. Supreme Court ruled that mandatory life terms without parole for juveniles were unconstitutional, and this fall it will hear a case on whether to make that decision retroactive for adult prisoners who committed their crimes as juveniles. But prosecutors and victims' rights advocates say youths still must be held accountable for their crimes and judges should be able to refer repeat and violent offenders to adult court. Forming a backdrop to the debate is neuroscientific research on adolescent brain development that indicates juveniles' reasoning abilities and impulse control are limited well into their 20s. The research also suggests that they can change their behavior, raising questions about youths' culpability and likelihood of rehabilitation.